1. Calculation of Background PM 2.5 Values
A Paper Review
Colin Boswell

2. Overview Problems Defining Background Historical Paper Reviews
Current EPA definitions
Compliance with Standards
Paper Reviews
Hidy and Blanchard 2006
Liu et al 2009
Conclusions

3. Problems US
Transport of PM from other continents contributing to base level PM. (ie. African and Asian Dust Storms)
Lead to non-compliance for local and regional standards
Unhealthy Air for “clean” areas
Globally
Transport of Pollutants from developing countries to others leading to poor health
Anthropogenic backgrounds
Climate Change Impacts

4. Defining Background (1)
Characteristic Conditions.
Surrogate background concentration range estimated from surveys of PM and PM composition data collected sporadically during observational campaigns in various remote marine or continental locations that represent apparent global, hemispheric, or intercontinental background conditions in the troposphere.
Natural Background.
Hypothetical conditions in the atmosphere representing PM concentrations and composition exclusively from natural sources, without emissions from human activities.
Background.
Intercontinental distributed atmospheric concentrations of PM and composition representing the cumulative effect of worldwide natural source emissions and human activities

5. Defining Background (2)
Unmanageable Background.
Background conditions in the continental United States defined for purposes as the rural-remote PM concentration and composition measurements on a regional spatial scale of hundreds of kilometers, potentially affected by regional distributions of natural and diffuse human sources, the latter exemplified by cumulative agricultural and de-minimus level urban practices and forest ecosystem management.
Baseline Levels.
Concentrations of PM and their composition represented by contemporary, sustained observations at continental remote-rural locations.

6. Historical (1)
EPA determines a need to generate background characteristics for PM
Staff Papers determine that background PM is defined as non-sulfate part of PM 2.5 measurement
15-20 ug/m3 is the upper end of daily PM2.5 background

7. Historical (2) With this background is compliance possible?
Standard is 15 ug/m3
EPA’s suggestion for keeping track
“Over shorter periods of time (e.g., days or weeks), the range of background concentrations is much broader than the annual averages. Specific natural events such as wildfires, volcanic eruptions, and dust storms, both of U.S. and international origin, can lead to very high levels of PM comparable to, or greater than, those driven by man-made emissions in polluted urban atmospheres. Because such excursions can be essentially uncontrollable, EPA has in place policies that can remove consideration of them, where appropriate, from attainment decisions”
Summarized - meaning the EPA has the absolute right to decided whether or not attainment could have been met based on obvious background interference or an uncommon natural event.

8. Hidy 2006 (1) Background is more complex than EPA has defined it.
Bases the study of of the IMPROVE network
Filters out all IMPROVE stations that have above average national PM 2.5 values.
Separates Rural and Urban Location
Separates sites based on latitudes

9. Hidy 2006 (2)

10. Hidy 2006 (3)

11. Hidy 2006 (4)

12. Hidy 2006 (4)
Quantify data as west of the Mississippi and east of the Mississippi.
West Background ug/m^3
East Background 4-10 ug/m^3
Leads to regional appointment of PM values over a broad area.
Values used state that all rural IMPROVE sites are only background emissions
The values do not take into consideration separation of foreign or domestic contributions.
i.e. unmanageable background vs. global background

13. Liu et all 2009 (1)
Develops a model to describe and characterize background PM 2.5 sources on a global scale.
Comparing a 7-year average of model results with various observational data for sulfate, BC, OC, and dust, and then place our results in the context of previous modeling studies.
Separates Continents and there individual inputs as well as intercontinental PM interactions.
Takes into consideration large scale random events
i.e. volcanoes, wildfires, biomass burning, dust storm*

14. Liu et all 2009 (2)

15. Liu et all 2009 (3)

16. Conclusions Background effects Background Calculations
Standards and health effects to other areas
Non compliance of areas when they do not produce all of the emissions
Background Calculations
EPA
Simplistic and unable to alter standards
Hidy
Better assumptions for emissions but areas are quantified too much
Liu et all
Complex modeling with correlation to 7 years of data is the best option for generating background values